Electrothermostatic switch



ELECTROTHERMOSTATIC SWITCH Filed Dec. 24, 1925 I VENTOR wr m ifflTTORIVEYS Patented July 24, 1928.

PATE oFFi E.

UNITED STATES NIG'HOLA J. LUTTBELL, OF LIVERPOOL, NEW YORK.-

ELECTBOTHERMOSTATIC swrrcn.

Application filed December 24, i925. Serial No. 27,491.

The main object is to provide a compact and comparatively inexpensiveswitch of this to character havmg a wide range of uses in which theheating of the electrical resistance for opening the switch may beattributable to different causes but will have the same effeet and stillserve different purposes.

The specific object is to make a switch of this type from two springterminals having cooperative contacts and arranged in such manner thatthe one terminal is pressed into contact with the other for closing thecircuit, both contacts will be moved in the same direction but inintersecting arcs and when the pressure is released the contacts willautomatically interlock with each other to hold the circuit closed.

Another specific object is to provide one of these terminals wit-h athermostatic bar and an electric resistance coil, both connected inseries with the secondary switch terminal in such manner as to form anelectric switch in which the heat developed in said resistance willcause a deflection of the thermostatic bar and secondary switch terminalsufficientto release it from interlocking engagement with the primaryterminal and thereby to automatically open the switch for breaking thecircuit Other objects and uses relating to specific parts of the devicewill be brought out in the following description.

In the drawings:.

Figure 1 is an enlarged longitudinal sectional view of a double switchadapted to be used for controlling directional signals of automobilesand other vehicles.

Figure 2 is a diagrammatic view of the same switch and lighting circuitsfor direc tional signals v Figure 3 is a diagrammatic view of a singlethermally controlled electric switch connected in a motor circuit andadapted to be automatically opened (after being closed manuallyyby heatdeveloped in the resistance due to overload upon the circuit.

Figure 4 is adiagrammatic view of a single switch as used in thecharging circuit of a storage battery "for preventing overloading of thebattery.

The double thermostatic switch shown in Figures 1 and 2 is adapted to beused for controlling the circuits to a pair of incandescent electriclamps, -hand -R or other electrically operated translating devices whichare connected in branch circuits --a'- and -a;' of a main circuit Aderiving current from a source of electric energy as a battery -B--.

This double switch comprises a pair of flat spring terminals 1 and --1-,an additional pair of fiat spring terminals 2- pair of thermostatic bars3 and -3' and electric resistance coils .l and 4', the terminals of eachpair being secured at one end to an insulating support -5- so as toextend in opposite directions therefrom and normally in spaced parallelplanes under their own tension.

The free ends of the terminals at either side of their insulatingsupport -5- cooperate to open and close the circuit throughitscorresponding signal independently of the other set of terminals andconstitute cooperative contacts and 7- and 6 and 7.- slightly varyingdistances from their insulating support 5' so that they may be sprung ordeflected under pressure relatively to said support for closing thecircuits through their respective signals -R and The spring terminals 1and 1 are preferably formed in one piece secured midway between its endsto the insulating support -5 for economy and compactness, the centralportion thereof being connected to one side of the battery B- forsupplying current to both switches.

The contact members 7 and 7'- are offset toward their companion contactmembers 6 and 6'- to form shoulders with which their companion contactmembers 6 and 6' are adapted to engage when depressed for closing thecircuit through the corresponding translating devices.

The inner ends of the spring terminals 2 and -2 are secured in insulatedrelation to the support 5- to extend laterally in opposite directionstherefrom and in spaced parallel relation to the corresponding terminalsl and 1- so as to permit their respective contact members 'Z, to yieldwhen the free ends of the adjacent till? terminals 1- and -1'-- ;arepressed against them.

It isnow evident that the free ends of both sets of terminals may bedeflected from their normal positions by pressure upon the free ends ofthe terminals 1- and 15- and by contact of those terminals with the freeends of the terminals -2- and.2'- thereby causing the contact members ofeither set to move in diflerent intersecting arcs as H and bbrespectively, Figure 1.

The contact members 6 and 6 normally project slightly beyond theircompanion contact members 7 and 7'- so that when depressed toward theirrespective terminals 2 and 2' they will first engage the adjacent facesof their corresponding shoulders 7 and -'-7 and, as the pressure iscontinued the-terminals 2 and 2- will be also deflected in the samedirection until the edges of the companion contact members reach theintersection of their respective arcs of movement a-a and bb whereuponthe end faces of said contact members will snap into engagement witheach other and will be held in such engagement by.the tension of theirrespective terminals tending to return to thelr normal positions untilreleased in a manner presently described. I a

This release may be effected manually by simply depressing the free endsof the terminals 2 and 2-- when interlocked with-the free ends of theiradjacent terminals -1 and -1- and for this purpose the free ends of theterminals 2- and -2 are provided with extension finger This release ofthe interlocked contact members 6 and 7-- or -6'- and 7- may also beeffected automatically by heat developed in the corresponding coils 4-or t"- which are wound upon the thermostatic bars 3- and 3'-respectively and are electrically connected in series with theirrespective signals. -R' and L---- and corresponding switch terminals-2'- and 2'. I

These thermostatic bars -3- and 3'-- are preferably made of electricconducting spring leaves of different coefficients of expansion and havetheir inner ends secured to the inner ends of their respective switchterminals 2- and -2 for electrical connection therewith, the outer endsof said closed and released for energizing and dey thermostatic barsbeing arranged to engage the inner faces of suitable ledges '10- and 10on the free ends of the terminals 2 and 2'. v

These thermostatic bars 3- and 3' are arranged so that their free endswill be deflected against their respective ledges -.-10 and .10'+- whensubjected to heat under a predetermined temperature for auto maticallyopening either switch after being closed in the manner described.

The resistance coils 4- and 4-- are electrically connected at one end totheir respective thermostatic bars -3 and -3 and have their other endselectricalfy connected to their corresponding signals -R and L, saidresistance coils being constructed aiid'arranged so that when eitherswitch is closed and held in its closed position in the mannerpreviously explained for an approximately predetermined interval of timethe corresponding coil will become heated to such an extent as todeflect its thermostatic bar against the adjacent ledge as 10- orv 10thereby efiecting a corthe manner described it will remain closed untilsufiicient heat is developed in the corresponding coil to cause itsthermostatic bar to automatically-release the switch terminals frominterlocking engagement with each other and permit the automatic openingof the switch.

For example, if it is desired to energize the signal-R-ito indicate aright hand turn the free end of the terminal 1 will be depressed by thepush button 9- sufliciently to cause interlocking engagement between thecontact members 6 and -7- which will close the circuit through the.resistance coil 4-.

The contact members 6- and 7- will be automatically. held closed in themanner described thereby maintaining a closed circuit through the coil'4- for an appreciable interval vof time according to the constructionand arrangement of the coil or until the thermostatic bar 3- has beenheated and deflected sufficiently to release the switch terminals fromsaid interlocking engagement whereupon the terminals will open under:their own tension to break the circuit thereby relieving the operatorfrom the necessity of opening the circuit manually after the periodrequired for the energizing of the signal.

In like manner the other switch may be energizing its correspondingsignal -L--. In Figure 3 is shown a single switch for automaticallybreaking a motor circuit in case of an overload thereof.

The motor as M may be connected to any source of electric'energy forsupplying current thereto through the medium of wires W--, said circuitincluding therein one of the electric switches, previously described,including the heater coil 4 and thermostatic bar 3, the coil 4- beingconnected in series between the motor M- and switch terminal 2.

Otherwise the construction of the switch is substantially the same asthat previously described except that the terminal 2- is provided withan extension -8 for engagement by a push button 9- for releasing saidterminal from engagement with the terminal -1 while the other terminalis engaged by a similar push button -9 for closing and locking theswitch.

In Figure 4 is shown a similar switch connected in the, charging circuitC for a storage battery and adapted to be operated in a manner similarto either of the switches shown in Figure 2 except that in case ofoverload of the battery the heat developed in the coil 4 willautomatically release the interlocking terminals from their closedposition and allow them to open for breaking the circuit.

The operation of the switch, in so far as it relates to the lockingengagement of the terminals by pressure of one against the other forclosing the circuit and the automatic release of the terminals fromengagement one with the other through the heating of the coil -4- andconsequent deflection of the thermostatic bar -3 for opening the switch,is substantially the same in the several uses described, the onlydifference being in the circuits in which the switch is connectedaccording to the different uses.

\Vhat I claim is:

1. An electric switch comprising two flat spring terminals normallysupported at one the same direction, one of said terminals having ashoulder offset toward the other terminal, the end of said otherterminal being extended slightly beyond the shoulder tovabut againstsaid shoulder and thereby to automatically hold the terminals inelectrical contact when the pressure is released.

2; An electric switch comprising a pri mary spring terminal and asecondary spring terminal, both of said terminals being supported at oneend in normally spaced parallel relation and insulated one from theother and having their other ends free to yield transversely underpressure, the free end of the secondary terminal being provided with ashoulder offset toward the end of the primary terminal, said primaryterminal being extended slightly beyond the shoulder whereby deflectionof the free ends of both terminals in one and the same direction bypressure of the primary terminal against the secondary terminal willcause the end of the primary terminal to abut endwiseagainst theshoulderof the secondary terminal for holding the terminals inelectrical contact when the pressure is relieved. K

3. An electric switch as in claim 2 having heat controlled meansoperable under a predetermined temperature for causing the release ofthe engagement of one terminal with the other.

4. An electric'switch as in claim 2 in which a thermostatic bar isoperatively connected to the secondary terminal for automaticallywithdrawing the same from engagement with the primary terminal whensubjected to heat under a predetermined temperature, and an electricheater connected in the switch circuit adjacent said thermostatic barfor heating the same.

In witness whereof I have hereunto set my hand this 21st day ofDecember, 1925.

NICHOLAS J. LUTTRELL.

